Mass spectrometry reproducibility evaluation

Owing to its stability, solubility, and highly reproducible oxidation behavior, ferrocene has long been used as an electrochemical standard in nonaqueous solvents. Not surprisingly, the electron-donor or -acceptor properties of ring substituents in ferrocenes and other metallocenes have been repeatedly evaluated with electrochemical techniques. Measurements have been obtained using polarography,150 cyclic voltammetry (CV),151 chronopotentiometry,152 photoelectron spectroscopy, 53 and Fourier transform ion cyclotron resonance mass spectrometry.154 Extensive compilations of such data are available.155 156 Historically, variations of oxidation potentials have been discussed almost solely in terms of the... 

The results are reported of a study of plate-out in PVC extrusion carried out using several analytical techniques, including DSC, SEM-EDX, FTIR spectroscopy and laser ionisation mass spectrometry. A special die and calibrator unit developed to investigate plate-out are illustrated and the reproducibility of the method evaluated. The effects of water content and anti-plate-out additives, such as alumina and silica, on plate-out are discussed and mechanisms explaining the formation of plate-out are proposed. 11 refs. 

Mass spectrometry has become more useful In the support of electronic development and manufacturing processes. Fourier transform mass spectrometry, the latest advance in this analytical method, Is another step forward in versatility, sensitivity and reproducibility in analytical characterization, qualification and quantification of raw materials and contaminants as used in electronic devices. A review will be provided of basic instrument hardware and interfacing, significant operating parameters and limitations, and special inlet systems. Emphasis will be placed on material evaluation, process control and failure analysis. Data handling will be reviewed using appropriate examples encountered in material and failure analysis. 

Matrix effect and matrix suppression/enhancement are terms in bioanalysis that are often used interchangeably. However, the matrix effect is a more specific terminology in bioanalysis and is primarily used to describe whether an assay s performance can be reproduced for individual subject samples, regardless of the difference in matrices. If the response ratio of an analyte to its ISTD can be kept consistent under the same concentration level in different matrices, then no adverse matrix effect can be claimed for the bioanalytical assay. On the other hand, matrix suppression/enhancement is more explicit to evaluate whether an analyte signal is affected by coeluted matrix components even though they are not directly measured by mass spectrometry. The suppression/ enhancement can be ascribed to an analyte s ionization efficiency, which is impacted, either negatively or positively, by the underlying matrix components. 

Molloy, M. P Donohoe, S. Brzezinski, E. E. Kilby, G. W. Stevenson, T. L Baker, J. D. Goodlett, D. R. Gage, D. A. Large-scale evaluation of quantitative reproducibility and proteome coverage using acid cleavable isotope coded affinity tag mass spectrometry for proteomic profiling. Proteomics 2005, 5, 1204-1208. 

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